A day in the life of a U.S. Border Patrol agent is a never-ending flow of migrants and smugglers

They call it a wall, but technically, it's a fence albeit an imposing one.And in Nogales, Ariz., it's impossible to miss.

Eight metres tall in most places, it slices through the town along the international border between the United Statesand Mexico. On a directive from U.S. President Donald Trump, the fence is now fortified with coils of razor wire, installed earlier this year.

And still they come: migrants, families fleeing strife in Central America and drug smugglers who all find a way through, over, under and around the infamous wall.

It's a frustrating fact of life for U.S. Border Patrol agents.

"We know that if you build a 100-foot wall, they're going to bring a 101-foot ladder," saidJake Stukenberg, one of the agents stationed in Nogales, about 100kilometres south of Tucson, Ariz.

But, he said, at least the wall slows them down.

Stukenberg agreed to spend a daywith CBC News earlier this monthwhile patrolling the 50-kilometre section of border his unit is responsible forto underline the challenges inherent in policing a barrier that faces a seemingly never-ending flow of migrants and smugglers determined to get across no matter what.

About 1,000border crossers are caught trying to cross the borderin Stukenberg's district every week, he says.

Those fleeing strife typically seek out agents andimmediately claim asylum. Stukenberg says he sees plenty of people like that, including a group of more than100one day this month. But, he says, a key focus for Border Patrol isthose who try to avoid capture.

Drug smuggling has long been a big part of the cross-border challenge in Arizona. In years past, the smuggled drug of choice was marijuana, but Stukenberg says, lately, they increasingly seefentanyl, the powerful opioidbehind a rash of overdose deaths in recent years in the U.S. and Canada.

And despite the imposing nature of the wall, smugglers are adept at breaching it.

"This is one spot where they cut it," saidStukenberg, pointing at one of the visible gaps in the razor wire left by those who climb up and use cutters to snip a pathway for those who want to get to the other side.

At that point, the race is on.

"It is literally seconds from the time that someone jumps over that fence right there, puts their feet on the American soil and runs up to those areas," saidStukenberg, pointing at a nearby Nogales industrial park.

"And there's a million hiding places in there. So, it's literally 30 seconds before they could be in a hiding place. Good luck finding him after that."

On the day CBC News spent with Stukenberg, agents in his jurisdictiondetained 154 suspected undocumented migrants.One such detention happened just a block from Border Patrol offices, as CBC News drove up to meet with Stukenberg.

Evidence of the migrants is everywhere. Abandoned clothing is seen tangled in the razor wire;there are clear handprints on the bollard-style fencing, left by those who've climbed up and over; and seemingly everywherethere is fencing, there are also abandoned water bottles left by those who had travelled through the desert just to get to that border.

Stukenbergsays he leaves politics to thepoliticians, but he doesn't hide the fact he's very much pro-wall. Trump has vowed to buttress and extend existing barriers, de facto creating a wall along the full length of the more than 3,000 km long U.S-Mexico border.

Stukenbergsays the fence along his stretch of the border makes his work easier simply by impeding those who want to cross illegally, even if it doesn't always stop them.

"Give us the tools necessary to do our job," he said.

What's his broader answer to the challenge of dealing with all themigrants and smugglers?

"If I had a magic wand?" he said."I would eliminate the cartels from the face of the Earth.

"Then you get rid of the No. 1facilitator for narcotics into our country.You get rid of the No. 1facilitator for illegal immigration. You get rid of the No. 1facilitator for corruption in other countries."

But Stukenberg isn't holding his breath.

Patrolling down below

Meanwhile, as he patrols the border along the dirt roads that parallel the wall, other agents train for illegal crossings of another kind underground.

Fellow agent Kevin Hecht took CBC News into a faux smuggling tunnel constructed as a subterranean training ground.

It's buried about two metres underneath a parking lot at the Border Patrol headquarters in Nogales.It's dark, cramped, filthy and instructive.

"It's all belly-crawl," saidHecht, highlighting how narrow it can be inside the actual tunnels.

Smugglers will often dig through dirt until they reach municipal water drainage tunnels, then break in and shimmy into the U.S.

So, patrolling agents are on the lookout for cuts in the tunnel walls.

"You have to go and look at the pipe, look for any change in the pipe," said Hecht.

Scuff marks can signal patched-over places where smugglers have installed, in effect, doorway flaps.

"And behind it will be an illicit tunnel that you can crawl through across the border. That's what they call interconnecting," he said. "And then once you're in this pipe, you're on the U.S. side of the border."

Drugs come in through the existing water drainage tunnels, but agents in Nogales also come across tunnels that are fully dug by hand, including one just this past May.

Back on top, Stukenberg signalled toward a grassy hill on the Mexican side of the wall.

"I absolutely would be amazed if we're not being watched right now," he said.

Spotters regularly keep watch on Border Patrol agents, he says, waiting for their vehicles to leave a particular location before instructing drug or human smugglers to make their jump over the wall.

"The smugglers will sit on this hill," he said, pointing, "[and]guide people with cellphones."

Soon enough, Stukenberg sees movement in some faraway bushes.

"I'm spotting a scout right now," he said."Under a tree. Two people, three people."

And suddenly, theyappear, making their way down the hill and toward the border fence.Border agents watch and wait. But then the people disappear into a gully.

"They're definitely smugglers, or being smuggled," saidStukenberg.

It could be hours yet before they try to cross.

"They're cartel," he said. "They have a big budget, and they have all the time in the world."

But as Stukenberg waits, his radio crackles with word from other agents patrolling another part of Nogales who are suddenly caught in a car chase involving suspected human smugglers.

Stukenberg puts his vehicle in gear and scrambles to go help.

"They've bailed out of the vehicle and are running into the desert," he said, spinning his vehicle around at the border walland heading into town, all the while knowing the spotters on the other side will quickly take note and relay word to whoever was down in that gully.

It happens all the time, he says.